The invention relates to clinometers (also known as inclinometers) and accelerometers, and more particularly to such devices that utilize a conductive, freely movable material to contact both a conductor and a resistor to define the resistance of the resistor as a function of the inclination of the apparatus or the acceleration thereof, and more particularly to such that devices capable of producing an essentially continuous variable output signal representing up to 360 degrees of rotation.
Quite a variety of electronic clinometers and accelerometers have been proposed. For example, U.S. Pat. No. 2,893,134 discloses a clinometer in which a conductive ball is supported by an arcuate conductor and an arcuate linear resistor. The arcuate conductor thereby carries a voltage representing the amount of voltage division across the arcuate resistor at the point at which the conductive wall contacts it. This signal is fed into an amplifier, the output which is utilized to control self-leveling of a scraper blade. The device subtends an arc of roughly 80 degrees. U.S. Pat. No. 4,493,155 discloses a device for providing a remote indication of the angular position of rotatable equipment, wherein a hollow cage member is affixed to the rotatable equipment. The inner surface of the cage is supplied with a series of electrically conductive surfaces, the positions of which are known in relation to the orientation of the cage. A conductive rolling member contained within the cage is free to move under the influence of gravity and contacts the lowermost pairs of conductive surfaces. Sensing devices detect the pair of surfaces currently in electrical communication by virtue of the position of the conductive rolling member, providing a stepped indication of rotational orientation. U.S. Pat. No. 4,503,622 discloses a clinometer that utilizes a bubble level of the electrolytic type partially filled with a suitable conductive liquid and provided with electrical contacts within the bubble container. A differential signal is produced across the electrical contacts when the level is tilted. U.S. Pat. No. 4,167,818 discloses a device in which a ball movable around a 360 degree toroidal race capacitively couples signals between signal source and signal collector electrode assemblies provide on opposite sides of the toroidal race. U.S. Pat. No. 3,584,387 discloses a slope indicating device in the form of a carpenter's level wherein a conductive sphere disposed in an annular chamber produces contact between predetermined electrical conductors when the level is disposed precisely at preselected angles.
None of the prior clinometers/accelerometers is an inexpensive device that provides essentially continuous electrical output signals up to 360 degrees of rotation of the device and is capable of operating at very low levels of electrical power consumption to provide a precise digital readout that indicates both positive and negative angles of inclination or the direction of acceleration. Some of the prior devices that utilize conductive balls in a race are likely to produce inaccurate results if the device is subjected to vibration, as the conductive ball will bounce, repetitively making and breaking electrical contact with contact point the location of which represents the angle of inclination or the amount of acceleration, or making contact with numerous "illegal" contact points.